1. Field of the Invention
The present invention relates to a resource control system and a resource control method for packet mobile communication and relates to a base station and a mobile station suitable for use in the same.
2. Description of the Related Art
In packet mobile communication using CDMA (Code Division Multiple Access), a capacity of an uplink radio channel is determined based on maximum allowed receiving power of a base station, and a capacity of a downlink radio channel is determined based on a maximum transmission power of the base station. In the packet mobile communication using CDMA, when transmission power control (TPC) is carried out, the received power (uplink direction) of the base station or the transmission power (downlink direction) of the base station is determined in accordance with an amount of interference received by the base station or the mobile station.
However, in the conventional packet mobile communication as described above, as the amount of interference received by the base station or the mobile station increases, the possibility increases that the total received power (uplink direction) of the base station exceeds the maximum allowed receiving power thereof and the total transmission power (downlink direction) of the base station exceeds the maximum transmission power thereof.
Therefore, there is a problem in that packet transmission fails or packet transmission becomes impossible between the base station and the mobile station, and packet discard or packet transmission delay is caused.
In order to solve such a problem, in conventional packet mobile communication, a technique performing Qos (Quality of Service) control has been known.
In a packet mobile communication performing the conventional Qos control, the base station individually performs resource control, like allocating resource to high priority users, in accordance with the amount of interference, the amount of resources (radio carrier frequency, time slot, code, etc) of an own cell, and the traffic priority of users in its own cell.
However, in the packet mobile communication performing the conventional Qos control, since the base station or mobile station performs the resource control individually in accordance only with the amount of interference from other cells, the amount of resources of the own cell, and the traffic priority of the own cell, the resource control is not intended to perform in cooperation with the resource control of other cells.
Therefore, there is a problem in that the Qos cannot be improved and the resources cannot be efficiently utilized from the point of view of the whole packet mobile communication system.
For example, as shown in FIG. 1, when real time users A to D are concentrated in a cell 1 and non-real time users G and H are concentrated in a cell 2 adjacent to the cell 1, in a case where downlink traffic in the cell 1 is in a state of congestion, each of mobile stations 10A to 10E receives a large amount of interference. Accordingly, each of mobile stations 10A to 10E requests transmission power (downlink direction) at high level to the base station 301.
As a result, even when the base station 301 of the cell 1 preferentially allocates available resources to the real time users (for example, the users A to C) as done by conventional Qos, the base station 301 cannot transmit packets directed to some real time users (for example, the user D). Therefore, in the cell 1, packet discard occurs because a delay time of packet transmission exceeds an allowable delay time thereof in some cases.
On the other hand, in the adjacent cell 2, since the number of real time users (for example, the user F) is small, the base station 302 of the cell 2 has enough margin in the allocatable resources even after transmitting the packets to the real time user F in the own cell. Accordingly, the base station 302 can transmit the packets (non-real time packets) directed to the users G and H up to the maximum transmission power of the base station 302.
As described above, in the case where real time packets cannot be transmitted in the cell 1 while even non-real time packets can be transmitted after real time packets are transmitted in the cell 2, there is a problem of lowering satisfaction of the Qos and the resource utilization efficiency with regard to the entire service area in the packet mobile communication system.
Especially, in a micro cell with a small cell diameter and a cell for fourth generation mobile communications, the mobile stations are often unevenly distributed in each service area, and the above described problem becomes marked.